In an assisted-global positioning system (A-GPS) or assisted-global navigation satellite system (A-GNSS), a GPS receiver, when operational in a particular wireless network, receives and uses location-related assistance data to improve its performance, e.g., in terms of time-to-first-fix (TTFF) value and position accuracy. But typically, in such systems, the GPS receiver (e.g., a GPS-capable cellular device) is able to request for and retrieve location-related assistance data from only a location-information source in the wireless network where the device is operational.
Even if multiple sources or servers storing location-related assistance data are available to or accessible by the GPS receiver/device, it may be restricted to choose only one of the sources to receive the assistance data. Moreover, assistance data from two different sources may be incompatible or unsynchronized, such that they are not usable by the device to compute the position/location. For example, one source in the wireless network may provide proprietary information of the network, such as network time, position, etc., as assistance data. And, another source (e.g., a location server in the same or different network) may provide assistance data including data related to a satellite constellation selected by the network. In such a case, the device may not be able to utilize the two sets of dissimilar data, and may have to select one of the two sets for computing the position of the device.
In another example, the device may be a cellular device capable to connecting to different cellular networks, e.g., networks of different cellular operators (AT&T, Verizon, etc.), or networks implemented with different cellular technologies (e.g., 3G, 4G (WiMAX, LTE), etc.). In case the device transitions its connectivity from one network to another (e.g., due to roaming, simultaneously connecting on two different data networks, or voluntarily switching from one network to another), in current assisted-positioning systems, the device has to terminate its current position-computation session which may be using assistance data from the previous network, discard the previous assistance data, and initiate a new position-computation session in the new network, and request and use new assistance data. Thus, the device lacks the opportunity to use assistance data from multiple location-information sources (e.g., by integrating previous and new assistance data) to further improve its performance.